Method of and apparatus for annealing metal bodies



March 23, 1965 F. D. HAZEN r-:TAL

METHOD OF AND APPARATUS FOR ANNEALING METAL BODIES Filed Feb. 19, 1963 INVENTORS United States Patent METHOD 0F AND APPARATUS FUR ANNEALING METAL BODIES Frank D. Hazen and Howard H. Nichols, Pittsburgh, Pa., assignors to Hazen Engineering Company, Pittsburgh,

Pa., a corporation of Pennsylvania Filed Feb. 19, 1963, Ser. No. 259,703 4 Claims. (Cl. 148-16) This invention relates to a method and apparatus for annealing metal bodies such as castings, fittings, sheets and the like, and more particularly to the yannealing of aluminum.

Aluminum is annealed at relatively low temperatures varying from 800 to 1200 F. and is handled on trucks which are pushed into an annealing chamber, which chamber is closed during the annealing period.

Aluminum, when exposed to radiant heat, becomes discolored and one of the ditiiculties is to supply necessary heat to the annealing chambers Without exposing the aluminum product to radiated heat.

Heretofore heat has been supplied to the annealing chamber from the top or bottom of the chamber in the form of hot air which has been passed over a heating element before it enters the annealing chamber. One of the difficulties experienced was that the heating elements were disposed in line with the aluminum products whereby the latter were exposed to radiant heat even though the heating element was separated from the annealing chamber by a partition wall.

In accordance with the present invention, these diiiiculties are overcome by heating the annealing atmosphere such as air or inert gases7 at a point remote from the heating chamber and completely separated and insulated therefrom so that the product to be annealed is not exposed to radiated heat.

lt is among the objects of this invention to provide a method of annealing aluminum and other castings by charging the aluminum product into an annealing chamber through which hot air or inert gases at suitable annealing temperatures are passed and caused to circulate entirely around the product.

It is a further object of the invention to supply the heated air or gases through a perforated wall on one side of the aluminum product to be annealed, under pressure, and removing it through a similar perforated wall on the opposite side of the load to be annealed. The air is supplied under pressure of sutiicient force and velocity to cause a partial vacuum to occur yadjacent the perforated Wall from which the heated air is emitted to set up great turbulence and circulation of the hot air With-in the annealing chamber and the heated air or gases are removed through the other perforated wall of the chamber by means of a fan or blower to aid in forcing circulation throughout the annealing chamber.

Still a further object of the invention is to provide an annealing structure in which the heating elements are mounted outside of the annealing chamber and is disposed in relation to a source of air such that the air passes -in wiping contact with the heating element to a chamber having a perforated partition dividing it from the annealing chamber.

These and other objects of the invention will become more apparent from a consideration of the accompanying drawing constituting a part hereof in which like reference characters designate like parts and in which:

The single figure is a vertical cross-sectional view, partially in elevation, diagrammatically illustrating an annealing chamber and heater embodying the principles of this invention.

In the drawing, the numeral 1 designates the rails of 3,174,83 Patented Mar. 23, 1965 a track on which is mounted a car 2 having a door 3 supported by wheeled axles 4 on the track 1. The car 2 may be a iiat car with closed ends and open sides and also an open top and the products such as aluminum castings can be stacked on the iioor 3 to till the car. The numeral 5 designa-tes the roof of an annealing chamber7 the latter having perforated sheet metal walls 6 and 7 with perforations 8 and 9 and having outer Walls 10 and 11 that extend all the way down to the base of the track 1 so that when the car 2 is placed in the annealing chamber and a door, not shown, is closed, the door being of the full dimension of the roof 5 and side walls 6 and 7, the bottom is sealed when the door is closed.

The roof 5 is provided With a passage or duct 12 which communicates with the air compartment designated by the numeral 13 at one end and with a duct 14 that is connected to a fan or blower 15 which exhausts the air compartment 16.

The heater is a self-contained unit that burns a gaseous fuel supplied through a valve fuel line 18 and which has an air inlet 19 and -a Waste gas exit 20. The products of combustion of the heater 17 do not mingle with the air circulated from the header box 21 through duct 12, compartment 13, the annealing chamber, thence compartment 16 and through the fan or blower 15.

The air flow through the duct 12, the air compartments 13 and 16 and to the Kair header 21, is shown by arrows and the desired pressure of air which determines the velocity or rate of flow is controlled by the fan or blower 15.

The temperature of the air delivered through the perforated side wall '7 to the annealing chamber is controlled by the radiant heating tubes 17, of which there may be any number disposed in `a single or multiple duct system with suitable manifold connect-ions and the air passes from chamber 13 through the perforations 9 of the wall 7 at such a rate that a partial vacuum is created along the annealing chamber side of the wall 7. This, of course, causes an unbalance of the pressure in the annealing chamber which sets up turbulence and circulation of the hot air throughout the chamber to contact the product mounted on the oor of the car 2. The air is withdrawn from the annealing chamber through the perforations 8 ion wall 6 on the opposite side of the car 2 and is recirculated by fan 15, as shown.

It will be noted that there are no heating elements exposed to the walls 6 and 7 of the annealing chamber and that there is a very heavy insulating section in the roof 5 that prevents heat by radiation to pass to the annealing chamber` For this reason, the load on the car 2 is exposed to uniform heating throughout and there is no discoloration of the annealed product.

It is evident that the hot air entering through the perforations of Wall '7 in the main Will pass directly across the load on the car 2 and be also subjected to turbulence so that all of the surfaces of the stacked products are reached and it is further evident that the rate of annealing may be controlled by the volume of hot air that is passed through the annealing chamber in a given time.

Although one embodiment of the invention has been herein illustrated and described, it will be evident to those skilled in the art that various modifications may be made in the details of construction without departing from the principles herein set forth.

We claim:

1. The method of annealing metal products in an annealing chamber in which the products to be annealed are disposed between a pair of parallel perforated walls forming air compartments on each side of said annealing chamber and in which a heating element is disposed in a passage communicating with said air compartments which comprises;

(a) conducting a heating medium under pressure through the connecting passage and around said heating element to o ne of said yair compartments and through the perforatiens ,of one of said parallel walls into the said annealing chamber',

(b) withdrawing the heated air from said chamber through the perforations of the other of said parallel walls into the :other of said air compartments, and,

(c) exhaust-ing the heating medium from said secondnamed compartment and causing it to circulate ythrough the connecting passage in contact with the heating element disposed therein.

2. The method of annealing metal products as set forth in claim 1 in which the heated air is forced from the first-named of said perforated parallel Walls under sucient pressure to create a vacuum on the annealing chamber side of the furnace wall to cause turbulence and circulation of the heated air in the annealing chamber.

3. T he method as set forth in claim 1 in which the time of annealing the product is controlled by the total volume of heated air transmitted through the annealing chamber.

4. Apparatus for annealing metal bodies which consists compartments with adjacent outer walls of said chamber and having a support for the products to be annealed in the center of said furnace spaced from said walls, a flow passage for a heating medium connecting said air compartments, heating means disposed in said i'low passage, a source of a gaseous annealing medium and means for drawing said medium through said flow passage in heat exchange relation with said heating means and delivering the same to one of said air compartments and through the perforated wali of said compartment into the annealing chamber and withdrawing the same through the perforations of the other of said walls from said chamber into the other of said air compartments and means for recirculating said Withdrawn annealing medium through said ow passage in contact with said heating means.

References Cited by the Examiner UNITED STATES PATENTS 2,029,176 1/ 36 Lindberg 266,-5 2,228,564 1/41 Guthrie 266-5 2,311,350 2/43 Richardson 1587 3,109,877 11/63 Wilson 266-5 of walls forming an annealing chamber having a pair of 25 DAVID L. RECK, Primary Examiner.

spaced juxtaposed perforated walls forming spaced vail- 

1. THE METHOD OF ANNEALING METAL PRODUCTS IN AN ANNEALING CHAMBER IN WHICH THE PRODUCTS TO BE ANNEALED ARE DISPOSED BETWEEN A PAIR OF PARALLEL PERFORATED WALLS FORMING AIR COMPARTMENTS ON EACH SIDE OF SAID ANNEALING CHAMBER AND IN WHICH A HEATING ELEMENT IS DISPOSED IN A PASSAGE COMMUNICATING WITH SAID AIR COMPARTMENTS WHICH COMPRISES; (A) CONDUCTING A HEATING MEDIUM UNDER PRESSURE THROUGH THE CONNECTING PASSAGE AND AROUND SAID HEATING ELEMENT TO ONE OF SAID AIR COMPARTMENTS AND THROUGH THE PERFORATIONS OF ONE OF SAID PARALLEL WALLS INTO THE SAID ANNEALING CHAMBER, 